The power of microgrids

Why is there a lot of research and commercial interest in microgrids right now? Mitchell Lennard explains.

The term ‘microgrid’ covers a large range of energy system architectures. Researchers with a background in utility-scale electrical engineering tend to refer to any system smaller than, for example, the Victorian state grid, as a microgrid. At the other end of the scale, many designers see remote area power systems (RAPS) as the best representation.

The Microgrids at Berkeley project, one of the centres of excellence in this area of research (building-microgrid.lbl.gov), uses the following definition.

“Microgrids are electricity distribution systems containing loads and distributed energy resources (such as distributed generators, storage devices or controllable loads) that can be operated in a controlled, coordinated way either while connected to the main power network or while islanded (disconnected from the grid).”

This definition covers a wide range of system capacities and technologies. It certainly covers the sorts of systems that ATA members have been perfecting over several decades. It could even cover power systems in ships and aircraft.

The main reason there is growing interest in microgrids is that many of the generating technologies referred to as renewable (think PV, small wind, small hydro, solar thermal, wave) are all suited to and in some cases best used in microgrid or distributed energy system configurations.

The 2009 CSIRO report A Value Proposition for Distributed Energy in Australia concluded that: “In general, distributed generation appears to be an effective early action greenhouse gas mitigation option for Australia when it is considered within a portfolio of other mitigation options…but before distributed energy achieves wide-scale uptake, technology and market development needs to be focused on reducing costs and improving reliability.”

This notion that distributed energy systems and microgrids are a quick way to get greenhouse advantageous renewable generation into the energy mix is the main driver for most microgrid development work presently underway.

While it is possible to categorise microgrids in a range of different ways (have a look at the Berkeley site for one such set of definitions) the main projects running around the world can be seen as falling into two broad categories: campus-scale and remote-area microgrids.